El Nino means business

ClaireAnderson

Posted 11 September 2015 - 02:35 AM

ClaireAnderson

New Member

Members

63 posts

LocationSan Francisco, CA, USA

According to the NOAA forecasters, the world's greatest weather maker El Nino is in place and will peak at the end of this fall or the beginning of winter. Its' intensity will be reduced by March next year. What sort impact do you expect to sea due to El Nino this time around?

But the answer is more complicated. The interplay of all the different kinds of warming going on in the Pacific at the moment can be difficult to sort out and, as with the recent hurricane, attributing a weather event to a single cause is unrealistic.

Gabriel Vecchi, head of the climate variations and predictability group at the geophysical fluid dynamics laboratory of the National Oceanic and Atmospheric Administration in Princeton N.J., likened the challenge to the board game Clue.

“There’s all these suspects, and we have them all in the room right now,” he said. “The key is to go and systematically figure out who was where and when, so we can exclude people or phenomena.” Extending the metaphor, he noted that criminal suspects could work together as accomplices, and there could be a character not yet known. And, as in all mysteries, “You can have a twist ending.”

At the moment, the world’s largest ocean is a troublesome place, creating storms and causing problems for people and marine life across the Pacific Rim and beyond. A partial list includes the strong El Niño system that has formed along the Equator, and another unusually persistent zone of warm water that has been sitting off the North American coast, wryly called “the Blob.”

And a longer-term cycle of heating and cooling known as the Pacific Decadal Oscillation may be switching from a cooling phase to a warming phase. On top of all that is the grinding progress of climate change, caused by accumulation of greenhouse gases generated by human activity.

Each of these phenomena operates on a different time scale, but for now they appear to be synchronized, a little like the way the second hand, minute hand and hour hand line up at the stroke of midnight. And the collective effects could be very powerful.

Although they interact with one another, each of these warming events is being blamed for specific problems.

“The Blob” has been associated, among other effects, with the unusually dry and warm weather in the western United States. Out in the ocean, the nutrient-poor warmer waters of the Blob — about four degrees Fahrenheit higher than average — are disrupting the food web of marine life. Some species of fish are showing up where they are not expected, including tropical sunfish off the Alaska coast, and an unusual number of emaciated sea lion pups and Guadalupe fur seals are being found stranded on California shores.

The warm water has also been linked to unprecedented harmful algal blooms along the coasts that have rendered shellfish toxic and shut down shellfish fisheries in Washington, Oregon and California. “A single clam can have enough toxins to kill a person,” said Vera L. Trainer, the manager of the marine biotoxin program at NOAA’s Northwest Fisheries Science Center in Seattle. Officials also ordered the largest closure of the state’s Dungeness crab fishing.

“It’s really worrisome,” Dr. Trainer added. “If this is a single event that then goes away and we can forget about it down the road, it’s O.K. If it’s a window into the future, it’s not a good future.”

The other large force at work, the Pacific decadal oscillation, is a long period — sometimes, as the name implies, spanning decades — of relatively cooler or warmer water. Since about the year 2000, the oscillation has been in a cool state, which many climate scientists say has allowed the ocean to soak up a great deal of the heat generated by greenhouse gases as part of climate change.

This, in turn, may have kept global average surface temperatures from rising. Climate scientists have called that condition the warming hiatus, and those who deny the overwhelming scientific consensus on warming have used the hiatus to raise doubts about whether climate change exists.

Now, however, the oscillation appears to be entering a warming phase, said Gerald A. Meehl, a senior scientist at the National Center for Atmospheric Research, and strong El Niños tend to nudge the cycle into a new phase. So the oscillation and El Niño “can all add together to give you a really big shift” toward warming over all.

Climate change could nudge all of the interacting cycles of ocean heat and cold. Scientists are still trying to determine its effect on hurricanes, though it is widely believed that because warm ocean water provides the energy for hurricanes, the more powerful storms will grow even more potent over time.

Whether there is a clear and detectable human-caused component to today’s cyclone activity is harder to prove, said Thomas R. Knutson, a research meteorologist with NOAA’s geophysical fluid dynamics laboratory at Princeton. “We don’t expect to necessarily be able to detect these changes at this time,” he said.

While no individual weather event can be linked to climate change, the continued warming already appears to be increasing the potential strength of storms, said Kerry Emanuel, a hurricane expert at the Massachusetts Institute of Technology. Whether the storms reach their full potential depends on other factors, he said. Statistically, however, there are too few storms to show that the stronger hurricanes are being caused by climate change yet.

One phenomenon appears to be the result of a combination of El Niño, the Blob and climate change. NOAA this year announced that the world was in the midst of only the third global coral bleaching event ever recorded. Severe bleaching can lead to the death of reefs, and the loss of habitat for marine life and shoreline protection from storms. The current event began in 2014 in the Pacific and has persisted into this year, with the Blob’s effects being felt most keenly near Hawaii, where the western tail of that large patch of warmed water extends.

“This is absolutely the worst that they have ever seen,” said C. Mark Eakin, the coordinator of NOAA’s Coral Reef Watch. “It’s only the third time they’ve seen mass coral bleaching in Hawaii; the last time was last year.” And because El Niño events stretch from one year’s winter into the next spring, “we’re very likely to see the bleaching that’s going on this year go on into 2016 and even be worse in 2016,” he said.

A warmer Pacific also means higher seas at the United States coastline, because warm water expands and the general winds that flow from west to east will push water against the shore. That can add to an increase in what William Sweet, a NOAA oceanographer based in Maryland, calls nuisance flooding in low-lying coastal areas.

Even a general increase of a half a foot from El Niño can, when combined with storms, cause a pronounced increase in such flooding, he said, adding that San Francisco could go from an average 12 days of nuisance flooding to 21 this year, and La Jolla, Calif., from six to 10.

Nicholas A. Bond, a research meteorologist at NOAA’s cooperative institute at the University of Washington who gave the Blob its name, said that climate change could make El Niño conditions more common. “That would just have monstrous implications,” he said. And though developed-world nations like the United States could take measures to adapt to the changing conditions, “It is going to be a different place,” he said.

Despite all the current dark clouds over the Pacific, literal and metaphorical, Dr. Bond managed to spot a silver lining.

The confluence of problems can serve as a “wake-up call,” and a harbinger of climate change, he said. “We have a real chance with this kind of event to see what’s going to happen, and show folks, ‘Hey, this is the consequence of messing around with the climate.’ ”

One of the most powerful El Niños on record continues gathering strength and is looking increasingly likely to bring heavy rains to key Northern California areas that provide water for the rest of the state, according to a new forecast.

There are better odds that the area around Lake Oroville, California's second-largest reservoir, will have above-normal precipitation -- now more than a 40% chance, up from a more than 33% chance in last month’s forecast. San Francisco now has more than a 50% shot of a wetter-than-average winter, up from a more than 40% probability.

Los Angeles continues to have more than a 60% probability of a wet winter during the months of January, February and March. Officials are scrambling to prepare, including clearing out basins and making sure roads are ready for all the rain.

Is there any chance El Niño will suddenly collapse?

Not really. There is a 95% chance that El Niño will persist through the spring, the Climate Prediction Center says.

El Niño is a warming of ocean waters west of Peru that can cause dramatic changes to the atmosphere, altering weather patterns worldwide. In the past, it has meant that the path of winter storms that normally keeps the jungles of southern Mexico and Central America wet moves north, over California.

That pattern has traditionally meant drought in Central America and southern Mexico, and a wet winter for northern Mexico and the southern United States. (It has also meant the best surfing season in a generation, from the coast of British Columbia to Costa Rica.)

The pool of warm water in the Pacific Ocean west of Peru is huge and very deep. “There’s been a tremendous distribution of heat, and that is definitely not going away” any time soon, said Bill Patzert, climatologist with NASA’s Jet Propulsion Laboratory in La Cañada Flintridge. “I’m quite optimistic that the entire state is going to get hosed.

"This El Niño is so dramatically large. It’s so intense. It’s hard to imagine that it won’t deliver," Patzert said.

How big is this warm water in the Pacific Ocean west of Peru?

“It's about 8 million square miles of overheated ocean," Patzert said. "The United States is only 3 million square miles. So this is about two and a half times the size of the continental United States.

"This thing is pumping moisture out of the overheated ocean into the atmosphere above, which of course means it's having a huge impact and rearranging all the pieces on the weather board across the planet.”

Overall, what's the outlook for the ski season?

It will probably remain the best ski season in years, because ski resorts are so high in elevation. “The really high elevations in the Sierra Nevada will do well,” Stanford's Swain said.

But what about the mountains that are important to the state’s water supply?

No one has a good answer for this. The mid-elevation mountains of Northern California are very important to the state’s water supply, and it’s important that precipitation comes as snow, not rain.

Too much rain all at once will force excess water to be flushed out to sea to prevent dams from being overwhelmed. But if snow falls, it can melt slowly in the spring and summer, gently replenishing reservoirs.

Scientists generally agree that more precipitation is likely in these mid-elevation mountains. But whether it’ll fall as snow or rain isn’t known.

What have El Niño winters brought to California in the past?

A lot of rain, snow and devastation. Los Angeles in the 1997-98 season saw double the amount of rainfall, and the mountains of Northern California saw double the snowpack. The storms themselves were not particularly intense, but the problem was that there were so many of them and they came one after another at a relentless pace. Downtown Los Angeles in February 1998 saw nearly a year’s worth of rain in that single month.

That winter, 17 people died in California, and more than half a billion dollars' worth of damage occurred. Flood-control channels overflowed, mudslides destroyed hillside homes and roads, and railroad tracks were washed away.

What isn’t expected in an El Niño?

Patzert says Pineapple Express storms -- the kind that come from south of Hawaii and bring excessive rain in a short amount of time -- aren’t typically seen during an El Niño.

“They’re the storms where you get 10 inches in 24 hours. The El Niño storms aren’t like that,” he said.

An example of a Pineapple Express storm was the storm in 2010 that dumped rain at an alarming rate over the mountains that burned in the massive Station fire, unleashing a torrent of mud that inundated more than 40 houses in La Cañada Flintridge, Patzert said.

How hot is this El Niño?

Ocean waters west of Peru are now hotter than recorded in at least 25 years, surpassing the temperatures during the record 1997 El Niño. It is the highest such weekly temperature recorded in 25 years of modern record-keeping in this key region of the Pacific Ocean west of Peru.

Temperatures in this key area of the Pacific Ocean rose to 5.4 degrees above average for the week of Nov. 11. That exceeds the highest comparable reading for the most powerful El Niño on record, when temperatures rose 5 degrees above the average the week of Thanksgiving in 1997.

In fact, last week was the hottest this area of the Pacific Ocean has been since 1990, when records began being kept meticulously. It was 85.46 degrees as of Nov. 11, surpassing the 85.1-degree record hit a week before. Prior to that, the record high was 84.92 degrees set the week of Thanksgiving in 1997.

Will this El Niño end the drought?

That's virtually an impossibility. By one calculation, California’s mountainous north would need 2.5 times to three times its average precipitation to end this drought, and the record is only about double the average rain and snowfall.

A big question is also what comes after this El Nino ends -- and it could be renewed drought.

"My scenario is that the El Niño delivers as expected, and then El Niño switches to a La Niña, which is what happened in 1998," Patzert said, which brings drought. "It went into two years of below-normal snowpack and rainfall," and the start of a dry spell.

El Niño historically can't be counted on to keep California wet. The last big El Niño came 17 years ago, and they come too infrequently for California to rely on. California gets more of its water over a 25-year period from storms from the Gulf of Alaska and Pineapple Expresses instead.

"Over a 25-year period, over the long term, El Niño provides only 7% of our water. So as much as we’re hyping it, it’s not a big player," Patzert said. "It’s fast and furious, but it’s too irregular – the gap between El Niños is too long to build any statues to El Niño to be a drought-buster. If we were going to build a drought-buster statue downtown, it would be North Pacific storms or Pineapple Expresses."

Dan the Weatherman

Posted 20 November 2015 - 06:24 PM

Dan the Weatherman

Daily Contributor

Members

1466 posts

LocationOrange, CA

Due to the strength of this El Nino, I would expect to start seeing periodic storms in CA any time now. It seems that this season got off to a delayed start when it took until the middle of October to finally get out of the summer pattern (what I often refer to as "summer mode"). Normally we are out of "summer mode" by the beginning of October as we transition into fall. Storms during strong El Nino years often start sometime in November (in 1997 we had 4 storms during November with nearly 2" of rain downtown Los Angeles), but this month has been calmer and drier than normal so far. I believe the delay of the beginning of a true fall pattern to mid October has delayed the start of the rainy season this year here in Socal, and hopefully by the end of this month or the beginning of December, a wetter pattern finally emerges!

snow_wizard

Posted 22 November 2015 - 10:17 AM

snow_wizard

The Snow Wizard

Mods

13575 posts

LocationCovington, WA

I'm not sold on this Nino having all of the effects that people are expecting. At this point some key indices are completely backwards from they would normally be with any warm ENSO event let alone one of this scope. There is a massive pool of subsurface cold water rapidly moving eastward under the ENSO regions so I think it will collapse dramatically by late winter or spring. Once the collapse of the 1997-98 Nino began the SST anoms fell off a cliff.

Dan the Weatherman

+3.1 in nino 3.4 this week, pretty amazing. This nino is very shallow compared so some of the other big events, I agree that it dies off quickly at some point.

Do you think this El Nino is going to bring good rains to California, or is something completely different this time around that could cause the state to experience drier than normal conditions? I know you are studying meteorology right now, and I thought that I would ask you for your opinion on this.

I will say one thing is that I have not been impressed by this month so far as far as precipitation goes. The Sierra have received some snow, but it has been really dry here in Socal, especially in the Los Angeles Basin. November 1997 brought nearly 2" to Los Angeles and only a trace has fallen so far.